1. Field of the Invention
The invention pertains to the field of filter circuits, and more particularly to filters for reducing a.c. components (ripple) on direct current signals. 2. Description of the Prior Art
It is usually the requirement of a power supply to provide a relatively ripple-free source of d.c. potential from an a.c. line. A power supply, however, generally gives an output voltage which contains a.c. ripple components fluctuating about the desired d.c. potential. In the prior art, filters are inserted between the rectifier of the power supply and its output terminals to attenuate the rippe components to tolerable levels.
Filters employed for attenuating, the ripple components are generally of the type that utilize capacitors, inductors, or a combination of a capacitors and inductors to achieve the desired ripple reduction. In many power supplies these filters become relatively large and contribute appreciably to the size and weight of the unit. When filters utilizing only capacitors are utilized for power supplies having low ripple level requirements, the capacitance value must be high. Generally these capacitors are of large physical size, are heavy, are costly, and are difficult to package. When inductance is used to reduce the size of the capacitor, the ability of the resulting circuit to respond to rapid load variations is diminished.
The present invention provides a circuit for achieving low ripple levels with capacitors of moderate capacitance value and concomitant moderate size and weight.